Advanced Java Notes

Reflection inspects and manipulates classes at runtime. It powers most frameworks and should be rare in application code.

Java

A dynamic proxy implements an interface at runtime and routes every call through one handler, which is how cross cutting behaviour is added.

Java

Modules add a boundary above packages: a module declares what it needs and what it exposes, and everything else stays private.

Java

A sealed type names exactly which types may extend it, which lets the compiler check that a pattern switch covers every case.

Java

An immutable object cannot change after construction, which removes whole categories of bug at the cost of a little copying.

Java

What changed in each release since Java 8, which old habits it replaces, and what to reach for in new code today.